The present invention relates to a method of producing a water treatment medium or filter medium which can effectively deposit microorganisms and like suspended solids for purifying waste water or like fouled liquids, and a water treatment medium produced by the method.
A filter medium for cleansing waste water is required to have working surfaces provided with innumerable minute holes which allow passage of a mother liquor while preventing passage of suspended solids for causing them to be deposited or accumulated on the surfaces. In order to improve the filtering properties of the filter medium, the following requirements must be met.
(1) Increasing the number of the minute holes to provide a higher filtration speed, i.e., to increase the amount of the mother liquor passed.
(2) Enlarging the total area of the working surfaces to increase the amount of solids suspended or accumulated thereon, i.e., to provide a higher filtrability.
Typical filter media heretofore used for purifying waste water include filter paper, filter cloth, ceramic filters, and metallic screens. Since these media provide only a small overall working area for contact with a liquid to be filtered, they cannot afford sufficient capture of suspended solids, hence a low filtrability. Further, attempts to enhance the filtrability of these media would result in an undue reduction in the filtration speed.
Japanese Published Examined Patent Application No. 56-35926 discloses a medium for selective drainage of water which consists of fiber lumps packed in a cylindrical metal net, each fiber lump comprising a multiplicity of staple fibers intertwined or entangled with one another. Although prepared for a different purpose, the fiber lump, if used as a filter medium, can meet the foregoing requirements and eliminate the drawbacks of the conventional filter media. However, the method of making such fiber masses according to this prior art is extremely cumbersome and inapplicable to quantity production, and the product obtained thereby is of low quality. More specifically, this prior art provides a dry-type method in which a multiplicity of staple fibers are first subjected to a special crimping process which may require chemical treatment, heating or application of steam to obtain fixedly crimped fibers. The crimped fibers are then introduced into a cylindrical container in which the fibers are dispersed in air and agitated by a rotary drum having a plurality of agitating blades so that the fibers are intertwined with each other to form spherical fiber lumps.
In the method of this prior art, the fibers are agitated in air and are thus less likely to flex and intertwine with each other since The Young's modulus of the fibers in air is rather high and since air cannot impart complicated movement due to its low viscosity. Thus it is necessary to crimp the fibers before agitation to help the fibers intricately to tangle with each other during the agitating operation. Further, since the clearance formed between the cylindrical container and the rotary drum is extremely small, the amount of staple fibers processed at a time is limited, hence inapplicable to quantity production. Still further, since the fibers are invariably hit directly by the agitating blades, the individual fibers will be greatly damaged and the surfaces of the fiber lumps will be unacceptably rough.
It is therefore an object of the present invention to provide a novel method which is adapted for quantity production and by which high-quality fiber masses are readily obtained, thereby providing an excellent filter medium which overcomes the drawbacks of conventional filter media.
To fulfill this object, the present invention provides a method of producing a water treatment medium comprising the steps of dispersing staple fibers in a dispersive medium liquid, and causing the fibers to flow and vibrate in the liquid so that the fibers are mutually intertwined or entangled to form spherical or spheroidal fiber lumps.
According to this method, since the fibers are immersed in a liquid, e.g., water, they readily flex due to a reduced Young's modulus. Further, since a liquid has a much higher viscosity than air, the fibers floating in the medium liquid flex intricately in line with the complicated movement of the liquid. Thus the fibers closely and complicatedly intertwine with each other in the medium liquid without the necessity of crimping them prior to agitation. Further, since the fibers float in the liquid, there is substantially no likelihood of the fibers being damaged as by a stirrer, thus ensuring a high quality of the formed fiber lumps.
According to a preferred embodiment of the present invention, an adhesive is added to the medium liquid so that the formed fiber lumps will not get disentangled.
The present invention also provides a filter medium produced in accordance with this novel method.
These and other features and effects of the present invention will be readily understood from the description of embodiments given with reference to the accompanying drawings.